The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An engine discharges thermal energy while generating torque based on combustion of fuel, and a coolant absorbs thermal energy while circulating through the engine, a heater and a radiator, and releases the thermal energy to the outside.
When a temperature of the coolant of the engine is low, viscosity of oil may increase frictional force and fuel consumption, and a temperature of an exhaust gas may increase gradually to lengthen a time for a catalyst to be activated, which degrades quality of the exhaust gas. In addition, as a time taken for a function of the heater to be normalized is increased, a driver of the vehicle may feel discomfort.
When the coolant temperature is excessively high, we have discovered that knocking is occurred and performance of the engine may deteriorate by adjusting ignition timing in order to suppress the knocking. In addition, when a temperature of a lubricant is excessively high, a viscosity of the lubricant is lowered and the lubrication performance may be deteriorated.
A water pump of the engine includes a mechanical water pump driven in proportion to the number of revolutions of the engine and a variable water pump capable of being controlled according to the engine and environmental factors regardless of the number of revolutions of the engine. The variable water pump may control the flow rate to improve warm-up performance, fuel efficiency, heating and cooling performance. Among the variable water pumps, the multistage control water pump may control the flow rate from 0% to 100% at the water pump speed proportional to the engine speed.
However, we have discovered that even if the flow rate of the coolant is controlled by the mechanical or variable water pump, the cooling system must be equipped with a mechanical or electronic thermostat and the coolant may flow through a radiator.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure, and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.